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Australian megafauna
Australian megafauna comprises a number of large animal species in Australia, often defined as species with body mass estimates of greater than 45 kg (100 lb)1 or equal to or greater than 130% of the body mass of their closest living relatives. Many of these species became extinct during the Pleistocene (16,100±100 – 50,000 years BC).2 There are similarities between prehistoric Australian megafauna and some mythical creatures from the Aboriginal dreamtime.3 Causes of extinction Edit Learn more The neutrality of this section is disputed. The cause of the extinction is an active, contentious and factionalised field of research where politics and ideology often takes precedence over scientific evidence, especially when it comes to the possible implications regarding Aboriginal people (who appear to be responsible for the extinctions).4 It is hypothesised that with the arrival of early Australian Aboriginals (around 70,000~65,000 years ago), hunting and the use of fire to manage their environment may have contributed to the extinction of the megafauna.5 Increased aridity during peak glaciation (about 18,000 years ago) may have also contributed, but most of the megafauna were already extinct by this time. New evidence based on accurate optically stimulated luminescence and uranium-thorium dating of megafaunal remains suggests that humans were the ultimate cause of the extinction of megafauna in Australia.67 The dates derived show that all forms of megafauna on the Australian mainland became extinct in the same rapid timeframe — approximately 46,000 years ago1 — the period when the earliest humans first arrived in Australia (around 70,000~65,000 years ago).5 Analysis of oxygen and carbon isotopes from teeth of megafauna indicate the regional climates at the time of extinction were similar to arid regional climates of today and that the megafauna were well adapted to arid climates.6 The dates derived have been interpreted as suggesting that the main mechanism for extinction was human burning of a landscape that was then much less fire-adapted; oxygen and carbon isotopes of teeth indicate sudden, drastic, non-climate-related changes in vegetation and in the diet of surviving marsupial species. However, early Australian Aborigines appear to have rapidly eliminated the megafauna of Tasmania about 41,000 years ago (following formation of a land bridge to Australia about 43,000 years ago as Ice Age sea levels declined) without using fire to modify the environment there,8910 implying that at least in this case hunting was the most important factor. It has also been suggested that the vegetational changes that occurred on the mainland were a consequence, rather than a cause, of the elimination of the megafauna.8 This idea is supported by sediment cores from Lynch's Crater in Queensland, which indicate that fire increased in the local ecosystem about a century after the disappearance of megafaunal browsers, leading to a subsequent transition to fire-tolerant sclerophyll vegetation.111213 Chemical analysis of fragments of eggshells of Genyornis newtoni, a flightless bird that became extinct in Australia, from over 200 sites, revealed scorch marks consistent with cooking in human-made fires, presumably the first direct evidence of human contribution to the extinction of a species of the Australian megafauna.14 This was later contested by another study that noted the too small dimensions (126 x 97 mm, roughly like the emu eggs, while the moa eggs were about 240 mm) for the Genyornis supposed eggs, and rather, attributed them to another extinct, but much smaller bird. The real time that saw Genyornis vanish is still an open question, but this was believed as one of the best documented megafauna extinction in Australia15 "Imperceptive overkill"; a scenario where anthropogenic pressures take place; slowly and gradually wiping the megafauna out; has been suggested.16 On the other hand, there is also compelling evidence to suggest that (contrary to other conclusions) the megafauna lived alongside humans for several thousand years.1718 The question of; if (and how) the megafauna died before the arrival of humans is still debated; with some authors maintaining that only a minority of such fauna remained by the time the first humans settled on the mainland.19 One of the most important advocates of human role, Tim Flannery, author of the book Future Eaters, was also heavily criticized for his conclusions. Category:Megafauna Category:Prehistoric animals of australia Category:Extinct animals of Australia Category:Australian megafauna Category:Prehistoric birds of Australia Category:Reptiles of Australia Category:Animals of Australia